1. Field of the Invention
The present invention relates generally to insect repellents. More particularly, the present invention relates to synergistic blends of insect repellents, and to non-toxic lotions and sprays using the synergistic blends which may be used on humans and animals, where the repellents are particularly efficacious in repelling mosquitos.
2. State of the Art
In an attempt to repel insects, people have turned to widely marketed lotions and sprays (e.g. Cutters, DeepWoods Off, and Tick Garde) which contain N,N-diethyl-m-toluamide (DEET) as their active ingredient. While DEET is an effective repellent, it is not particularly pleasing in smell, may sting when applied, and its use has a number of harmful side-effects to humans. DEET is injurious to eyes, mucous membranes, and sensitive skin. In addition, because DEET is absorbed through the skin, toxic systemic reactions may result as well. For example, in August 1989, the New York State Department of Health investigated five reports of generalized seizures which were believed to be associated with the topical application of DEET. Other symptoms and maladies associated with repeated exposure to DEET have included irritability, confusion, insomnia, encephalopathy, and coma. As a result, cautionary statements regarding use of DEET have been issued by the Centers for Disease Control and the states of New York, Connecticut, New Jersey, and Utah.
The potential hazards of using a product with DEET as an active ingredient suggests that there exists a great need for a comparably repellent product that is not dangerous to its users.
It is known that various herbal and floral extracts are useful in repelling insects. For example, citronella, is widely known as an insect repellent, although it is not nearly as effective as DEET.
The above-referenced U.S. Pat. Nos. 5,227,406 and 5,346,922 disclose a non-toxic, generally natural insect repellent product known as TREO.RTM. which includes terpineol ("T"), citronella ("C"), and one or both of rhodinol extra ("R") and geraniol ("G") as active ingredients provided in a conveying medium. The active ingredients are Used in small percentages, e.g. as little as 0.01%, preferably at between 0.05% and 0.08%, and preferably less than 1%, yet are synergistically efficacious, particularly against mosquitos and possibly against other insects such as Lyme-disease carrying ticks. The conveying medium can be a cosmetic moisturizer lotion, with or without a sun screen. For a spray, the conveying medium can be water or alcohol based. An attractive non-interfering fragrance is preferably provided as approximately 0.4% of the insect repellent product, and is capable of masking the fragrances of the actives because they are present in low concentrations. The lotion or spray is safely applied in liberal quantities to humans and animals without unpleasant side effects such as stinging. It was discovered in controlled studies that the combination of the terpineol, citronella, geraniol, and rhodinol extra ingredients is effective because of a synergistic interaction among the ingredients. It was also discovered that the sub-combination of the terpineol, citronella, and rhodinol extra ingredients, and the terpineol, citronella, and geraniol ingredients are also synergistic. Best results were obtained with TREO.RTM. having the following concentrations of ingredients: 0.06% terpineol, 0.05% citronella, 0.08% rhodinol extra, and 0.06% geraniol.
There have been reports in the literature that a plant derivative known as "Chinese crystal" is also an effective herbal insect repellent. Chinese crystal, a naturally occurring component of an essential oil obtained from China, is available from Shaw Mudge & Company, Stamford, Conn. under the name "Chinese Botanical I". It is a crystalline compound commonly referred to as 3,8 P Menthanediol (also known as 2-hydroxy a,a,4 trimethyl cyclohexane methanol and has a molecular structure as shown below in Diagram 1. ##STR1##